Electroplating is a common technique used in integrated circuit (IC) fabrication to deposit one or more layers of conductive metal. In some fabrication processes it is used to deposit one or more levels of copper interconnects between various substrate features. An apparatus for electroplating typically includes an electroplating cell having a chamber for containing an electrolyte (sometimes called a plating bath) and a substrate holder designed to hold a semiconductor substrate during electroplating. In some designs, the wafer holder has a “clamshell” structure in which the substrate perimeter rests against a structure called a “cup.”
During operation of the electroplating apparatus, a semiconductor substrate is submerged into the plating bath such that at least a plating surface of the substrate is exposed to electrolyte. One or more electrical contacts established with the substrate surface are employed to drive an electrical current through the electroplating cell and deposit metal onto the substrate surface from metal ions available in the electrolyte. Typically, the electrical contact elements are used to form an electrical connection between the substrate and a bus bar acting as a current source.
An issue arising in electroplating is the potentially corrosive properties of the electroplating solution. Therefore, in many electroplating apparatus a lipseal is used at the interface of the clamshell and substrate for the purpose of preventing leakage of electrolyte and its contact with elements of the electroplating apparatus other than the inside of the electroplating cell and the side of the substrate designated for electroplating.